Polymerisable compositions and organic light-emitting devices containing them

ABSTRACT

Compositions of a mixture of a thiol material and a material that contains a reactive unsaturated carbon-carbon bond that can be polymerised to form a charge-transporting or luminescent film are described, as is an organic light-emitting diode (OLED) device comprising at least one such charge-transporting or emissive layer that has been formed by polymerising a thiol material and an ene material. The process for forming such an OLED, including the deposition of a layer of material comprising the polymerisable composition, from solution, exposing said layer to actinic radiation through a mask, and then optionally developing said film to form a photopatterned film, is also disclosed.

This is the U.S. national phase of International Application No.PCT/GB03/00899 filed Mar. 3, 2003, the entire disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

Organic light emitting diodes (OLEDs) are an emerging displaytechnology. In essence an OLED (or organic electroluminescent device)comprises a thin organic layer or stack of organic layers sandwichedbetween two electrodes, such that when a voltage is applied, visiblelight is emitted. At least one of the electrodes must be transparent tovisible light.

There are two principal techniques that can be used to deposit theorganic layers in an OLED: thermal evaporation and solution processing.Solution processing has the potential to be the lower cost technique dueto its potentially greater throughput and ability to handle largesubstrate sizes. However, several manufacturing issues still have to beresolved before solution processing of OLEDs can fulfil its potential.In a multi-colour or full-colour display the emissive organic layersneed to be patterned according to the pixel layout. High-resolutiondisplays require a high-resolution pattern for the emissive layer. Todate, solution-processing techniques for patterning the emissive layerare far from ideal.

In many cases, the most efficient OLED devices have multi-layerstructures (fluorescent emitter: e.g. U.S. Pat. No. 5,719,467(Hewlett-Packard 1995), EP 0,921,578 (CDT 1998), U.S. Pat. No. 6,048,573(Kodak 1998), U.S. Pat. No. 6,069,442 (Kodak 1997), U.S. Pat. No.5,554,450 (Kodak 1995); phosphorescent emitter: e.g. WO 00/57676 andU.S. Pat. No. 6,303,238). Such multi-layer structures can be formed bythermal evaporation, but when solution-processing techniques are used,depositing a second layer may wash away the first layer.

It has been recognised that if a photolithographic technique could besuccessfully applied to the patterning of the organic layers in an OLEDthen this would offer many benefits. Photolithographic techniques areestablished in other industries and can give good resolution and highthroughput. However the attempts to use photolithography during theformation of the organic layers in OLEDs have all had only very limitedsuccess.

BASF (U.S. Pat. No. 5,518,824) discusses the principle of forming anOLED using a crosslinkable charge-transporting material. The proposedfunctional groups are acrylates, vinylethers and epoxides. The materialis deposited from solution, and then exposed to UV light, whichcrosslinks the material making it insoluble. Subsequent luminescent orelectron transporting layers can be deposited on top of the insolublelayer. BASF mentions that if the UV exposure is carried out through amask, then the exposed areas will be insoluble and the unexposed areasstill soluble, and developing (washing) this film in solvent will removethe unexposed material, leaving the insoluble patterned material.However, this patterning is not demonstrated. BASF discuss doping thefilm with a fluorescent dye or using a crosslinkable fluorescent dye(U.S. Pat. No. 5,922,481) to form the light-emitting layer. The ELdevice results reported by BASF from its crosslinked devices are verypoor. The two devices reported, which have crosslinked but un-patternedlight emitting layers, give light emission only at 87 V and 91 V,respectively, both of which are entirely unacceptable operating voltagesfor an OLED. Canon (EP 1146574 A2) also demonstrate an OLED with acrosslinked emissive film, but there is still no demonstration of apatterned emissive layer. Further, Bacher et al. (Macromolecules 1999,32, 4551-4557) demonstrated photo-crosslinking of a hole-transporting(acrylate derivative of triphenylene) material. They produced apatterned photo-crosslinked hole-transport layer on to which theydeposited an emissive layer (tris(8-hydroxyquinoline)aluminium: Alq₃),and made a functioning OLED device. However, they had not developed atechnique for photo-lithographically patterning the emissive layer, andunless the emissive layer can also be patterned, only a monochromedevice can be formed. The problem with acrylates in all the prior art isthat although the acrylates can give very high resolution in thepatterning process, they quench luminescence. The quenching offluorescence by carbonyl groups is well known (Becker, Theory andInterpretation of Fluorescence and Phosphorescence, Wiley Interscience,NY 1969).

Other authors suggest crosslinking materials by thermally-initiatedprocesses. While such processes do form insoluble films allowingsubsequent layers to be deposited on top, they do not allow patterningof the layer. IBM has a patent (U.S. Pat. No. 6,107,452) onthermally/photochemically-induced crosslinking of polymers for use, forexample, in light-emitting devices. No patterning was demonstrated.

Bayerl et al. (Macromolecules 1999, 20, 224-228) used crosslinkedoxetane-bisfunctionalized N,N,N′,N′-tetraphenyl-benzidine as thehole-transporting material in a two-layer device. However, they did notpattern the hole-transporting material. Further work on oxetanes byMeerholz et al. (WO 02/10129) uses cationic photopolymerization to formcrosslinked layers. In one instance the emissive layer was patterned.But in many cases the photoacid generated during the polymerizationwould attack other components of an OLED, in particular organometallicmaterials, and therefore such procedures would not generally beappropriate for the formation of patterned crosslinked emissive layersin OLED devices.

Photo-polymerisable thiol/ene systems are known for various applicationssuch as printing plates and protective coatings. In these priorapplications of thiol/ene systems the resulting polymers have beeninsulators. Most of the thiol/ene systems mentioned in the prior artcontain non-conjugated carbonyl groups rather than aliphatic thiols, asaliphatic thiols can retain a nasty smell. In particular PETMP(Pentaerythritol tetrakis(3-mercaptopropionate) is commonly used as thethiol component (e.g. U.S. Pat. No. 5,100,929 and U.S. Pat. No.5,167,882).

The present invention is directed to OLEDs that solve some of theproblems in the prior art.

SUMMARY OF THE INVENTION

The invention is about directed to a composition of a mixture of a thiolmaterial and an ene material that can be polymerized to form acharge-transporting or luminescent film.

The invention is also directed to an OLED comprising acharge-transporting or emissive layer that has been formed bypolymerising a thiol material and an ene material.

The invention is further directed to a process for forming such an OLEDthat includes depositing a layer of material comprising a thiol and anene, from solution, exposing said layer to actinic radiation (UV light,visible light, electron beams or X-rays), through a mask, and thenoptionally developing said film.

According to a first aspect of the invention there is provided acomposition comprising a mixture of at least one monomer with theformula:A-(X)_(n)  (1)

and at least one monomer with the formula:B—(Y)_(m)  (2)

where monomers of formula (1) are polymerisable with monomers of formula(2), n and m are integers greater than or equal to 2, such that n and mmay be the same or different, X is a group containing a terminal thiol,Y is a group containing a reactive unsaturated carbon-carbon bond, eachX may be the same or different, each Y may be the same or different, andA and B are molecular fragments such that at least one of A or B is anorganic charge-transporting or organic light-emitting fragment.

According to a second aspect there is a solid film comprising athermally-induced or radiation-induced polymerisation reaction productof a composition according to the first aspect of the invention.

According to a third aspect of the invention there is provided a solidfilm comprising a polymer with repeat unit-(A-Z—B—W)—  (3)

where A and B are as defined above, Z is the addition product of thethiol-containing group, X, and the group containing a reactiveunsaturated carbon-carbon bond, Y, and W is the addition product of thegroup containing a reactive unsaturated carbon-carbon bond, Y and thethiol-containing group, X.

According to a fourth aspect of the invention there is provided an OLEDdevice comprising, laminated in sequence, a substrate, a firstelectrode, a first optional charge-transporting layer, a light-emittinglayer, a second optional charge-transporting layer and a counterelectrode wherein at least one of the optional charge-transportinglayers and/or the light-emitting layer is according to the second orthird aspects of the invention.

In a further aspect of the invention there is provided a process forforming a charge-transporting or emissive layer in an OLED comprisingthe following steps:

i) depositing a film with a composition according to the first aspect ofthe invention ii) polymerising said composition by exposing said film toheat or actinic radiation, or more preferably visible or. UV light.

In yet a further aspect of the invention there is provided a process forforming a charge-transporting or emissive layer in an OLED comprisingthe following steps:

i) depositing a film with a composition according to the first aspect ofthe invention ii) exposing said film to actinic radiation, or morepreferably visible or UV light through a mask iii) washing the exposedfilm to remove any unexposed material.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention there is provided a composition comprising amixture of at least one monomer with the formula:A-(X)_(n)  (1)and at least one monomer with the formula:B—(Y)_(m)  (2)

where monomers of formula (1) are polymerisable with monomers of formula(2), n and m are integers greater than or equal to 2, such that n and mmay be the same or different, X is a group containing .a terminal thiol,Y is a group containing a reactive unsaturated carbon-carbon bond,each)(may be the same or different, each Y may be the same or different,and A and B are molecular fragments such that at least one of A or B isan organic charge-transporting or organic light-emitting fragment.

The term reactive unsaturated carbon-carbon bond means a group that willreact under the correct conditions with a thiol to form a thioetherlinkage. Reactive unsaturated carbon-carbon groups are those withcarbon-carbon double or triple bonds such as alkenes, alkynes andstrained ring systems. In contrast the unsaturated carbon-carbon bondsin an aromatic ring would not react with a thiol to give a thioetherlinkage and so are un-reactive groups. Reactive unsaturatedcarbon-carbon bonds are often located at a terminal position in thechain or branch.

X and Y are groups capable of undergoing free-radical inducedpolymerisation. Optionally, the free-radical induced polymerisation cantake place in the presence of a radical initiator. It is desirable thatthe resulting polymer is insoluble in a solvent that can be used to washoff the un-reacted monomers. Therefore, it is preferred that acrosslinked polymer network is formed, i.e. that n+m>0.4. The exposureto actinic radiation is preferably done in an inert atmosphere to avoidthe formation of peroxy groups in the polymer. Following washing ordeveloping of the film, the film may be dried or undergo otherpost-patterning treatment.

There may be other components in the film in addition to the thiolmonomer and the monomer containing a reactive unsaturated carbon-carbonbond. In particular there may be a radical initiator, a luminescentdopant, or a charge-transporting molecule in the mixture.

X and Y are groups capable of undergoing photo-initiated free-radicalinduced polymerisation. X is a group containing a terminal thiol. Y is agroup containing a reactive unsaturated carbon-carbon bond or part of anunsaturated strained ring system. For brevity such a group is sometimesreferred to as an ene. X and Y are preferably connected to A and B byspacer units. Under the correct conditions X and Y react to form athioether linkage. The reaction proceeds by a step growth mechanism, asillustrated in the reaction scheme below (Jacobine, Radiat. CuringPolym. Sci. Technol., 1993, 3, 219-68).

Here, for illustration, the ene is a double bond but it could be atriple bond or an unsaturated strained ring system. Initiation involvesthe formation of thiyl radicals. Then a thiyl radical attacks thereactive double bond, Y, to give a β-thioether carbon radical, whichthen abstracts a hydrogen from another thiol group, creating a new thiylradical, which can propagate the reaction. The thiol is effectivelyadded across the reactive double bond and the chain transferred, hencethe need for multi-functional monomers. If each monomer has twofunctional groups (n=m=2) then a linear polymer can be formed, if atleast one of n or m is greater than 2 then a crosslinked polymer can beformed.

In principle, as many X groups as Y groups should be present forcomplete reaction to occur, if one group is in excess then the excesswill remain un-reacted. However, as is well known, in a polymerisationreaction of multi-functional monomers assuming unlimited mobility notall functional groups react (P. J. Flory, J. Am. Chem. Soc. 1947, 69,2893), so it is not thought to be critical that the number of X and Ygroups is balanced.

The polymerisation reaction produce of the thiol monomer (1) and the enemonomer (2) is a polymer with repeat unit—(A-Z—B—W)—  (3)where A and B are as defined above, Z is the addition product of thethiol-containing group, X, and the reactive unsaturated carbon-carbonbond, Y, and W is the addition product of the reactive unsaturatedcarbon-carbon bond, Y and the thiol-containing group, X. Such a polymercomprises a further aspect of the invention.

If A and B have similar molecular weights, both A and B should containcharge-transporting or emissive groups, i.e. be functional. If A and Bhave dissimilar molecular weights, however, it would be possible for thehigh molecular weight (i.e. oligomeric) group to be charge transportingor emissive while the low molecular weight group is neither chargetransporting nor emissive. However, the resulting polymerised filmshould have electroluminescent or charge-transporting properties.

The fragments A and B can have different properties depending onrequired function of the photopolymer layer. In one embodiment, thephotopolymer functions as a charge-transport layer in an OLED. In thiscase preferably both fragments, A and B, should containcharge-transporting groups, unless one fragment has much highermolecular weight than the other in which case said fragment alone can becharge-transporting. In another embodiment the photo-polymer forms theemissive layer. In this case, one or both organic fragments can be alight-emitting fragment and the fragments that are not light-emittingare preferably charge transporting, so for example one of A or B is alight-emitting fragment and the other is a charge-transporting fragment.Alternatively neither fragment A nor B is light-emitting but thephotopolymer is used as a charge-transporting host matrix for anemissive dopant. If one fragment has much higher molecular weight thanthe other, said fragment alone can be charge transporting or emissive.It is also possible for an emissive dopant to be used with aphotopolymer host that is itself emissive, i.e. where at least one of Aand B is a light-emitting fragment.

The invention also provides an OLED device comprising, laminated insequence, a substrate, a first electrode, a first optionalcharge-transporting layer, a light-emitting layer, a second optionalcharge-transporting layer and a counter electrode wherein at least oneof the optional charge-transporting layers and/or the light-emittinglayer is a solid film comprising a polymerisation reaction product of acomposition comprising a mixture of at least two components with thefollowing formulae:A-(X)_(n) B—(Y)_(m),where monomers of one component are polymerisable with monomers of theother component, n and m are integers greater than or equal to 2, suchthat n and m may be the same or different, X represents a groupcontaining a terminal thiol and Y represents a group containing areactive unsaturated carbon-carbon bond, and A and B are molecularfragments such that at least one of A or B is an organiccharge-transporting or organic (visible) light-emitting fragment.

The invention also provides a method for making such an OLED, wherebythe charge-transporting and/or light-emitting film is made by theprocess of:

-   -   i) depositing a film with a composition according to this        invention    -   ii) exposing said film to actinic radiation, or more preferably        visible or UV light, optionally through a mask,    -   iii) optionally washing the exposed film to remove any unexposed        material to leave a pre-determined pattern.

In a typical type of OLED the first electrode is an anode, the firstoptional charge-transporting layer is a hole-transporting layer, thesecond charge-transporting layer is an electron-transporting layer, andthe counter electrode is a cathode. However in another embodiment thefirst electrode is a cathode, the first optional charge-transportinglayer is an electron-transporting layer, the second charge-transportinglayer is a hole-transporting layer, and the counter electrode is ananode. As is well known in the field there may be additional functionallayers in the OLED. If the light emitter is phosphorescent, it isparticularly beneficially that either the electron-transporting layeralso functions as a hole-blocking layer, or there is an additionalhole-blocking layer between the light-emitting layer and theelectron-transporting layer. A pixellated OLED display can either be apassive-matrix or an active-matrix display. In one embodiment the firstcharge-transporting layer is a polymerised film according to thisinvention. In a preferred embodiment the light-emitting layer is apolymerised film according to this invention. In an alternativeembodiment, both the first charge-transporting layer and thelight-emitting layer are polymerised films according to this invention.It would also be possible for the first charge-transporting layer, thelight-emitting layer and the second charge-transporting layer to all bepolymerised films according to this invention.

The light-emitting layer in the OLED is preferably patterned, that is asuitable photo-mask is used when the film is exposed to light. Thispatterning technique allows a multi-colour OLED to be formed. A keyadvantage of the thiol-ene system is that good resolution can beachieved when it is photo-patterned. A film that is capable of emittinga first colour is deposited, patterned and developed to form pixelscapable of emitting a first colour. At this stage, since the film of thefirst colour is insoluble, it allows a film of a material that iscapable of emitting a second colour to be deposited without disruptingthe first colour film. This second film is patterned and developed toform pixels capable of emitting the second colour. The process can berepeated to deposit a material capable of emitting a third colour. Ifpresent, it may be appropriate to pattern a charge-transporting layer,and this can be done using the same masking technique.

A solution-processing technique, such as spin-coating, ink-jet printing,dip-coating meniscus or roller coating, or other printing or coatingtechnique, or thermal-transfer method is used to deposit the thiol/enelayer which is to be polymerised.

As discussed above, the fragments A and B can containcharge-transporting units. Suitable hole-transporting materials containπ-electron rich moieties. Particularly suitable are triarylamines (forexamples see Shirota, J. Mater. Chem., 2000, 10, 1-25). Thecharge-transporting fragment A or B can be based on knownhole-transporting arylamine materials such as those with the formula

where Ar is an optionally substituted aromatic group, such as phenyl, or

and Ar₁, Ar₂, Ar₃ and Ar₄ are optionally substituted aromatic orheteroaromatic groups (Shi et al (Kodak) U.S. Pat. No. 5,554,450. VanSlyke et al, U.S. Pat. No. 5,061,569. So et al (Motorola) U.S. Pat. No.5,853,905 (1997)). Ar is preferably biphenyl. In the current inventionat least two of Ar₁, Ar₂, Ar₃ and Ar₄ are bonded to either a thiolgroup, X, or a group containing a reactive unsaturated carbon-carbonbond, Y. Ar₁ and Ar₂, and/or Ar₃ and Ar₄ are optionally linked to form aN containing ring, for example so that the N forms part of a carbazoleunit e.g.

Bipolar materials that can form a bipolar fragment A or B transport bothholes and electrons. Suitable materials preferably contain at least twocarbazole units (Shirota, J. Mater. Chem., 2000, 10, 1-25).

Electron-transporting materials that can form an electron-transportingfragment A or B contain π-electron deficient moieties. Examples ofsuitable π-electron deficient moieties are oxadiazoles, triazines,pyridine, pyrimidine, quinoline, and quinoxaline (Thelakkat, Schmidt,Polym. Adv. Technol. 1998, 9, 429-42). Specific examples include Alq₃[Aluminium tri(8-hydroxyquinoline)], TAZ(3-phenyl-4-(1-naphthyl)-5-phenyl-1,2,4-triazole) and OXD-7(1,3-bis(N,N-t-butyl-phenyl)-1,3,4-oxadiazole).

As discussed earlier, one of the fragments A or B may be neither chargetransporting nor luminescent, provided that the other is. If such afragment is going to be used, it is preferred that it has a relativelylow molecular mass and is the basis for a multi-functional monomer. Asuitable fragment is based on pentaerythritol. For example monomer (1)could have the formula C(CH₂O(CH₂)_(n)X)₄ where n is an integer from 1to 6, or monomer (2) could have the formula C(CH₂O(CH₂)_(n)Y)₄ where nis an integer from 1 to 6. A tetra-functional non-charge transportingthiol formed from the pentaerythritol fragment (see example 2) can becombined with a difunctional charge transporting ene to form across-linked charge-transporting film.

Light emission may be via fluorescence or phosphorescence.

According to IUPAC fluorescence is defined as spontaneous emission ofradiation (luminescence) from an excited molecular entity with theformation of a molecular entity of the same spin multiplicity. Suitablefluorescent light-emitting materials are many organic molecules andcomplexes of metals of group 2, 12, 13 or light d-block metals withorganic ligands. According to the colour of the light emission thesematerials can be divided into three groups, blue, green and redemitters.

Suitable fluorescent blue emitters are e.g. stilbenes, coumarins,anthracences (Kodak U.S. Pat. No. 5,972,247 (1999). Toshio et al (ToyoInk) EP 0765106 (1996)) and perylenes (So et al (Motorola) U.S. Pat. No.5,853,905 (1997). Lee et al (Motorola) U.S. Pat. No. 5,747,183 (1996)).Also suitable are blue-emitting aluminium complexes (Bryan et al (Kodak)U.S. Pat. No. 5,141,671. Van Slyke et al (Kodak) U.S. Pat. No.5,150,006)). Suitable green emitters are Alq₃ (Chen and Tang, Macromol.Symp. 1997, 125, 1-48), coumarins (Chen et al (Kodak) U.S. Pat. No.6,020,078) and quinacridone (Shi et al (Kodak) U.S. Pat. No. 5,593,788).Suitable red emitters are DCM and its derivatives (Chen et al, U.S. Pat.No. 5,908,581). The fluorescent material can be a molecular or dendriticspecies. For examples of suitable fluorescent dendrimers see Samuel etal. (WO 99/21935). The light-emitting material may be a dopant in thecrosslinked charge-transporting matrix (comprising charge-transportingfragments A and/or B), in which case the emission spectrum of thecharge-transporting matrix should overlap the absorption spectrum of thelight-emitting dopant. Alternatively, the light-emitting material may bemodified so that it is itself a monomer, i.e. the light emittingmaterial is the fragment A or B of a polymerisable material. The dopantcan be a single material or a mixture of compounds. The concentration ofthe dopants is chosen so as to maximise colour purity, efficiency, andlifetime.

According to IUPAC the term phosphorescence designates luminescenceinvolving change in spin multiplicity, typically from triplet to singletor vice versa. The luminescence from a quartet state to a doublet stateis also phosphorescence.

Suitable phosphorescent light-emitting materials are heavy transitionmetal complexes. In particular organometallic complexes of iridium forexample Ir(ppy)₃ (fac tris(2-phenylpyridine)iridium), which gives greenemission (see Baldo et al., Appl. Phys. Lett., 75 no. 1, 1999, 4), or(btp₂)Ir(acac) (bis(2-(2′-benzo[4,5-α]thienyl) pyridinato-N,C³⁺) iridium(acetyl-acetonate)), which gives red emission (see Adachi et al., Appl.Phys. Let., 78 no. 11, 2001, 1622) are suitable. It could also be acomplex of platinum, for example2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (PtOEP) whichgives red emission. The phosphorescent material can be a molecular ordendritic species. The light-emitting material may be a dopant in thecrosslinked charge-transporting matrix (comprising charge-transportingfragments A and/or B), in which case the charge-transporting can bebipolar, hole transporting or electron-transporting. Alternatively, thelight-emitting material may be modified so that it is itself a monomer,i.e. the light-emitting material is the fragment A or B of acrosslinkable material. The dopant can be a single material or a mixtureof compounds. The concentration of the dopants is chosen so as tomaximise colour purity, efficiency, and lifetime.

The concentration of the phosphorescent light-emitting fragment in thehost material should be such that the film has a high photoluminescentand electroluminescent efficiency. If the concentration of the emissivespecies is too high, quenching of luminescence can occur. Aconcentration in the range 0.01-49 molar %, is generally appropriate.

Preferred examples of thiol monomers and ene monomers, suitable for usewith a phosphorescent dopant, are shown in FIGS. 1 and 2, respectively.A di-functional monomer derivative of CBP used with a tri-functionalmonomer derivative of TCTA will form a crosslinked polymer.Alternatively a crosslinked polymer would be formed if both the thioland ene monomers were tri-functional derivatives of TCTA.

There is typically a spacer chain between the charge-transporting orlight-emitting moiety and the polymerisable thiol or the reactiveunsaturated carbon-carbon bond. Such a spacer improves the film formingproperties of the material, allowing good quality films to be depositedfrom solution. The spacer also aids the polymerisation process. Thespacer should not contain any carbonyl groups (including those in theform of esters, amides etc.). The spacer can comprise alkyl, ether,thioether, aryl, siloxane, amine or unsaturated groups, or heteroatomssuch as silicon, boron or phosphorus. In fact neither A-(X)_(n) norB—(Y)_(m) should contain any carbonyl groups.

Synthetic routes to form thiol-containing materials including thosestarting from thiourea, thiosulfate ions, thiol esters anddithiocarbamates can be found in S. Patai, Chapter 4, The Chemistry ofthe Thiol Groups, John Wiley & Sons, London 1974.

A synthetic route to alkene materials that have an ether linkage betweenthe reactive unsaturated carbon-carbon bond and the rest of themolecule, is via a nucleophilic substitution in the presence of base asshown in FIG. 2 (the step from compound 10c to compound 10). Synthesisof ethers, Houben-Weyl, Methoden der organische Chemie, V1/3, GeorgThieme Verlag, Stuttgart 1965.

Thiol-ene mixtures can be easily thermally-polymerized andphoto-polymerised. Photo-polymerization has the advantage that goodresolution patterned films can be obtained and hencephoto-polymerization is preferred for OLED applications. The reactiveunsaturated carbon-carbon bonds are preferably electron-rich or theyform part of a strained ring system. In this later case, reaction of theunsaturated carbon-carbon bond with a thiol will then release the ringstrain. The reactive unsaturated group consists preferably of anorbornyl or vinylether moiety, other useful enes consist of allylether,or unsaturated cyclic systems. For the thiol-ene systems there aresuitable initiators for activation by either UV light or visible light.For successful initiation, it is generally preferable to use awavelength of light that is absorbed by the initiator but not stronglyabsorbed by the other components of the film. In this way the initiatorfunctions well and photo-degradation of the film is minimised.

The thiol-ene systems mentioned here do not contain any carbonyl groupstherefore no quenching of luminescence is observed. Unlike previouslyproposed photo-polymerisable systems proposed for OLEDs the thiol-enesystems is unique in offering a combination of high-resolutionpatterning with minimum luminescence quenching.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows examples of charge-transporting thiols.

FIG. 2 shows examples of charge-transporting enes.

FIG. 3 shows the electroluminescence emission spectrum of the device inexample 1.

FIG. 4 shows the photoluminescence emission spectrum from a film of athiol and an ene doped with Ir(ppy)₃ before and after exposure to UV(example 1).

EXAMPLES Example 1 Synthesis of4,4′,4″-Tris(3-vinylcarbazol-9-yl)triphenylamine and4,4′,4″-Tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine

The outline for the synthesis of the materials 22 and 24 is given in thefollowing scheme.

Synthesis of 4,4,4″-Tris(carbazole-9-yl)triphenylamine (20)

Potassium carbonate (52.0 g, 383 mmoles) was dried under high vacuum inan oil bath at 220° C. with vigorous stirring for 90 minutes. Carbazole(20.9 g, 125 mmoles, previously recrystallised from toluene) andtris(4-bromophenyl)amine (20.1 g, 47 mmoles) were added and placed underhigh vacuum for 10 minutes. Anhydrous toluene (175 cm³) was then addedand degassed under high vacuum for 10 minutes. Palladium acetate (280mg, 1.25 mmoles) and tris-tert-butylphosphine (750 mg, 3.71 mmol) werethen added and the reaction mixture was degassed under high vacuum for10 minutes and then refluxed under nitrogen for 18 hours before beingallowed to cool. As TLC analysis showed some unreacted material,anhydrous toluene (100 cm³) was added and the reaction mixture wasrefluxed for a further 4 hours and then allowed to cool. The reactionmixture was diluted with hexane (500 ml) and the reaction mixture wasstirred at room temperature for a further 1 hour and the reactionmixture was filtered. The residue was washed with hexane (3×200 ml),water (5×200 ml) and hexane (3×200 ml). The residue was recrystallisedfrom toluene twice to give white crystals4,4′,4″-Tris(carbazole-9-yl)triphenylamine (20) (25.8 g, 74%) with amelting point 298-299° C.

Synthesis of 4,4′,4″-Tris(3-formylcarbazole-9-yl)triphenylamine (21)

Phosphorus oxychloride (11.5 ml, 19.0 g, 115 mmol) was added dropwise toa stirring mixture of N,N-dimethylformamide (4.78 ml, 4.51 g, 61.7 mmol)and 4,4′,4″-Tris(carbazole-9-yl)triphenylamine (TCTA) (20) (7.26 g, 9.81mmol) and the resulting mixture was stirred at room temperature for 5minutes then heated to 90° C. for 5 days. The reaction mixture waspoured into water (800 ml) and the flask containing the product wasplaced in the ultrasonic bath for 2 hours to break up the material. Themixture was stirred for 2 hours then filtered. The residue was washedwith water (500 ml) followed by hexane (500 ml) then dried at the pumpfor 2 hours. The crude product, a brown solid, was heated at reflux withacetone (3×400 ml), cooled to room temperature and filtered. The product4,4′,4″-Tris(3-formylcarbazole-9-yl)triphenylamine (21) (6.09 g, 75%)was obtained as a pale brown solid with melting point 225-227° C. (dec).

Found: C, H, N, Calculated for C₅₇H₃₆N₄O₃: C, 82.99: H, 4.40; N, 6.79.

¹H n.m.r.: (300 MHz, CDCl₃): δ (ppm) 7.36-7.57, m, 24H, aromatic H,9.97, d, 3H, J 9.10 Hz, aromatic H, 8.21, d, 3H, J 6.75 Hz, aromatic H,8.66, s, 3H, aromatic H; 10.10, s, 3H, CHO. λ_(max)(CH₂Cl₂): 233 nm (ε82 144/Lmol⁻¹ cm⁻¹), 291 (74 701), 332 (56 562).

Band gap: 3.31 eV. FTIR (solid): 3048, 2716, 1685, 1593, 1505, 1311,1232, 1185, 808, 766, 741, 728 cm⁻¹.

Synthesis of 4,4′,4″-Tris(3-vinylcarbazol-9-yl)triphenylamine (22)

Dry THF (20 ml) was added under nitrogen to a deoxygenated mixture ofmethyltriphenyl phosphonium bromide (10.5 g, 29.3 mmol) and potassiumtert-butoxide (3.28 g, 29.2 mmol) and the resulting mixture was stirredat room temperature for 15 minutes. The trialdehyde 21 (5.37 g, 6.51mmol) was added under nitrogen and the reaction mixture was stirred atroom temperature for a further 2 hours. When the reaction was complete(TLC on silica using dichloromethane as the eluent) the solvent wasremoved under reduced pressure and then suspended in dichloromethane.The crude reaction in dichloromethane was filtered through a silica plugusing 50% dichloromethane/hexane as the eluent. Recrystallisation of theproduct 22 was attempted using various solvents without success and theproduct was purified further by chromatography on silica using 50%dichloromethane/hexane as the eluent. The product4,4′,4″-Tris(3-vinylcarbazol-9-yl)triphenylamine (22) (4.11 g, 77%) wasobtained as a pale yellow solid with melting point 226-228° C. (gel).Found: C, 87.70; H, 4.93; N, 6.47. Calculated for C₆₀H₄₂N₄: C, 87.99;H,5.17; N, 6.84. ¹H n.m.r. (CDCl₃): δ (ppm) 5,22, dd, 3H, vinylic H,J_(cis) 10.83, J_(gem), 0.88 Hz: 5.79, dd, 3H, j_(trans) 17.56, J_(gem),0.88 Hz; 6.92, dd, 3H, vinylic H, J_(trans) 17.56, J_(cis) 10.83 Hz;7.30, td, 3H, aromatic H, J 7.90, J 1.17 Hz; 7.41-7.58, m, 24H, aromaticH; 8.12-8.17, m, 6H, aromatic H. λ_(max)(CH₂Cl₂):248 nm (ε 119504/Lmol⁻¹ cm⁻¹), 284 (102668), 328 (66573). Band gap: 3.40 eV. FT-IR(solid): 3043, 1625, 1599, 1505, 1457, 1311, 1227, 885, 808, 745 cm⁻¹.PL (solution): 393 nm. CIE co-ordinates (x=0.165, y=0.044).

Synthesis of4,4,4″-Tris[3-(2-acetylthio-1-ethyl)carbazol-9-yl]triphenylamine (23)

Thiolacetic acid was purified by distillation prior to use. Thiolaceticacid (5 ml) was added to trivinyl derivative (22) (1.60 g, 1.95 mmol)that had been cooled in ice. The reaction mixture was warmed to roomtemperature and AIBN (a few mg) was added. The resulting mixture washeated at reflux for 1 hour (until the reaction was complete by TLCusing DCM as the eluent. The excess thiol acetic acid was removed underreduced pressure and the product was dissolved in a minimum volume ofdichloromethane. The crude product was purified by chromatography onsilica using dichloromethane as the eluent. The product was obtained asa yellow film. Attempts were made to recrystallise the product withoutsuccess. The product was purified by chromatography once more using theabove-mentioned conditions. The product4,4′,4″-tris[3-(2-acetylthio-1-ethyl)carbazol-9-yl]triphenylamine (23)was obtained as a yellow solid (1.27 g, 62%) with melting point 128-130°C. Found: C, 71.67; H, 4.79; N, 4.81. Calculated for C₆₆H₅₄N₄O₃S₃: C,75.69; H, 5.20; N, 5.35. Calculated for C₆₆H₅₄N₄O₃S₃ (1 mol DCM): C,71.07; H, 4.98; N, 4.95. ¹H n.m.r. (CDCl₃): δ(ppm) 2.36, s, 9H, CH₃;3.08, t, 6H, CH₂S, J 8.25 Hz; 3.23, t, 6H, CH₂, J 8.25 Hz; 7.25-7.33, m,3H, aromatic H, 7.39-7.59, m, 21H, aromatic H, 7.98, d, 3H, aromatic H,J_(meta) 1.10 Hz; 8.13, d, 3H, aromatic H, J_(ortho) 7.07 Hz.λ_(max)(CH₂Cl₂): 240 nm (ε 109 958/Lmol⁻¹ cm⁻¹), 297 (52 652), 328 (43308). Band gap: 3.45 eV. FT-IR (solid): 3043, 2924, 1684, 1601, 1505,1484, 1456, 1311, 1271, 1230, 1128, 1104, 944, 745 cm⁻¹.

Synthesis of 4,4′,4″-Tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine(24)

The trithioester was dissolved in THF (20 ml) then was added to asolution of potassium hydroxide (1.28 g, 320 mmol) in water (20 ml). Theresulting mixture was heated at reflux for 2 hours. The reaction mixturewas cooled to room temperature and was acidified to ph 6 with a dilutesolution of HCl (0.1 M). The product was extracted into dichloromethane(3×40 ml) and the organic phase was washed with water (100 ml) and brine(50 ml), dried (MgSO₄) and filtered. The filtrate was evaporated todryness to give the crude product as a white solid. The crude productwas purified by chromatography on silica using dichloromethane as theeluent. The product of4,4′,4″-tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine (24)obtained was a white solid (528 mg, 53%) with melting point 185-188° C.Found: C, 76.72; H, 5.37; N, 5.96. Calculated for C₆₀H₄₈N₄S₃: C, 78.22;H, 5.25; N, 6.08. Calculated for C₆₀H₄₈N₄S₃ (1 mol H₂O): C, 76.72; H,5.37; N, 5.96). ¹H n.m.r. (CDCl₃, 300 MHz): δ(ppm) 1.45, s, 3H, SH J7.70 Hz; 2.91, q, 6H, CH₂S, J 7.70 Hz; 3.16, t, 6H, CH₂, J 7.42 Hz;7.22-7.34, m, 3H, aromatic H, 7.36-7.60, m, 21H, aromatic H, 7.97, d,3H, aromatic H, J_(meta) 1.10 Hz; 8.13, d, 3H, aromatic H, J_(ortho)7.07 Hz. λ_(max)(CH₂Cl₂): 245 nm (ε 100 508/Lmol⁻¹ cm⁻¹), 298 (57 145),330 (48 854). Band gap: 3.44 eV. FT-IR (solid): 3043, 2963, 2926, 2556,1601, 1505, 1484, 1456, 1310, 1262, 1229, 1103, 1064, 1014, 802, 769,742, 726 cm⁻¹.

Fabrication of a Phosphorescent Emitter Doped Photo-Crosslinkable OLEDfrom 4,4′,4″-tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine (24)and 4,4′,4″-tris(3-vinylcarbazol-9-yl)triphenylamine (22)

Ir(ppy)₃ (8 wt %) (3.4 mg),4,4′,4″-tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine (24) (19.3mg) and 4,4′,4″-tris(3-vinylcarbazol-9-yl)triphenylamine (22) (19.3 mg)were dissolved in pure chloroform at total concentration 7 mg ml⁻¹. Thesolutions were spun onto ITO coated glass substrates (previously cleanedby ultrasonication in commercial detergent and thorough rinsing with DIwater). Prior to spin-coating the dry ITO coated glass wasplasma-treated in an Emitech K1050X plasma unit (process gas oxygen, 100W, 2 min). Solutions were spun onto the ITO substrates at 2000 rpm withacceleration 500 rs⁻¹ for a total of 30 s giving an emitting organiclayer of thickness ca 50 nm. Films were then photopolymerized under aninert atmosphere (N₂) using a Hanovir UVA 250W UV source. The films wereirradiated for 6 minutes through a 5″×5″ glass photo mask (cut-off 360nm) giving a rectangular exposed area 15×20 mm. Overlap of this areawith ITO anode and deposited aluminium cathode defines active areasconsisting of 6 pixels measuring 4×5 mm. The photopolymerized films weredeveloped by rinsing with pure toluene, dried under a stream of drynitrogen and transferred to the evaporator (KJLesker) for completion ofthe OLED by evaporation of ETL/HBL and top electrode. TPBI deposited byvacuum evaporation formed the ETL/HBL (50 nm). LiF (1.2 nm) andAluminium (100-150 nm) deposited by vacuum evaporation formed thecathode.

Device performance:

-   0.9 cd/A (@103.5 cd/m²), 0.28 Im/W (@10.2 V), turn on voltage (ToV)    6.0 V-   Max EQE 1.0 cd/A (@40 cd/m², 0.36 Im/W, 8.6 V)-   Max PE 0.42 Im/W (@7.5 cd/m², 0.94 cd/A, 7.1 V)-   CIE coords. x=0.34 y=0.59-   The EL emission spectrum is shown in FIG. 3.

FIG. 4 shows the PL emission spectrum of a spin-coated film of thematerials, before and after exposure to UV light i.e. before and afterphotopolymerisation. The film was prepared from a solution containing 10wt % Ir(ppy)₃ and a 1:1 ratio of4,4′,4″-tris[3-(2-thio-1-ethyl)carbazol-9-yl]triphenylamine (24) and4,4′,4″-tris(3-vinylcarbazol-9-yl)triphenylamine (22). Thephotopolymerisation was carried out as described above.

Example 2

Synthesis of Materials

Synthesis of tetraallylpentaerythritol (NME1)

Procedure carried out as directed in literature:—

Nouguier R, Mchich M, J. Org. Chem. 1985, 50, (3296-3298)

Synthesis of tetrathiopropylpentaerythritol (MAT1)

This is a two-step synthesis starting from the material NME1.

i) Synthesis of Tetrathioacetylpropylpentaerythritol

2.0 g (6.74 mmol) of tetraallylpentaerythritol was added to a 10 mlround bottomed flask fitted with a stirrer. The reagent was cooled on anice-bath where 4.11 g (53.98 mmol) of freshly distilled thioacetic acidwas added in 1 ml portions. After the addition was complete 5 mg of AIBNwas added and the reaction mixture stirred for 15 mins. When the AIBNhad dissolved the reaction mixture was heated at 60° C. for 12 hours,the reaction being followed by T.L.C. The product of the reaction had anR_(f) of 0.05 in dichloromethane (DCM) on silica and an R_(f) of 0.9 inethanol. The excess thioacetic acid was removed from the reactionmixture under vacuum and the residue applied to a short silica column inthe minimum volume of DCM. The column was eluted with 500 mls of DCMfollowed by 500 mls of ethanol. The ethanol fraction was collected andthe solvent removed. 2.9 g of tetrathioacetylpropylpentaerythritol wasisolated as a pale yellow oil.

Yield-71.5%

¹H NMR (CDCl₃) ppm: 3.41 (triplet, 8H) 3.34 (singlet, 8H) 2.92 (triplet,8H)

-   -   2.32 (singlet, 12H) 1.80 (quintet, 8H)

I.R (cm⁻¹): 2866.28, 1686.37, 1353.64, 1098.61, 952.97

ii) Synthesis of tetrathiopropylpentaerythritol (MAT1)

1.8 g (2.99 mmol) of tetrathioacetylpropylpentaerythritol was added to10 ml of anhydrous THF in a 100 ml round bottomed flask and the mixturewas degassed with stirring. The reaction vessel was purged with nitrogenand 12.3 mls of 1.00M LiAlH₄ in THF was added dropwise. The reaction wasallowed to stir at room temperature for 18 hours, the reaction beingmonitored by T.L.C. (DCM as solvent) When the reaction was complete themixture was acidified to pH 3 with 0.1 M HCl and 50 mls of DCM added.The organic phase was collected, the aqueous phase extracted with 2×50mls of DCM. The organic phases were combined and extracted with 4×100 mlbrine and 2×50 ml of water. The organic phase was dried over sodiumsulphate, filtered and the solvent removed. The product was isolated asa pale yellow oil with a mass of 0.92 g.

Yield-71.2%.

The product was distilled on Kugelrohr apparatus to yield a mobilecolourless oil, B.P 230° C. @ 10⁻⁴ mbar.

¹H NMR (CDCl₃) ppm: 3.47 (triplet, 8H) 3.34 (singlet, 8H) 2.60 (quartet,8H)

-   -   1.84 (quintet, 8H) 1.38 (triplet, 4H)

I.R (cm⁻¹): 2864.30, 1368.40, 1100.51

Synthesis of 4,4′-bis(3-(allyloxymethyl)carbazol-9-yl) (10)

See scheme in FIG. 2.

I) Synthesis of 4,4′-bis(carbazol-9-yl)biphenyl (10a)

Phosphorus tert-butyl phosphine (880 mg, 4.35 mmol) in toluene (88 ml)was added under nitrogen to a deoxygenated mixture of carbazole (11.9 g,71.0 mmol), 4,4′-dibromobiphenyl (10.0 g, 32.11 mmol), sodiumtert-butoxide (23.2 g, 241 mmol) and palladium acetate (324 mg, 1.34mmol) in toluene (50 ml) and the resulting mixture was heated at refluxunder nitrogen for 10 days. The reaction mixture was cooled to roomtemperature and then diluted with more toluene (200 ml). The reactionmixture was filtered to removes sodium salt and the filtrate was removedall traces of the product. The filtrate was concentrated to dryness togive the crude product as a pale brown solid. The crude product waspurified first by chromatography on silica using dichloromethane as theeluent followed by recrystallisation from toluene. The material was thensublimed at 280-281° C. at 10⁻⁶ mm Hg to give the product4,4′-bis(carbazol-9-yl)biphenyl as an off-white solid with melting point280-281° C. (lit. m.p. 281° C.).

ii) Synthesis of the 4,4′-bis(3-formylcarbazol-9-yl)biphenyl (10b)

Phosphosphorus oxychloride (13 ml, 21.5 g, 140 mmol) was added dropwiseto a stirring mixture of N,N-dimethylformamide (5.40 ml, 5.10 g, 69.7mmol) and 4,4′-bis(carbazol-9-yl)biphenyl (7.72 g, 16.0 mmol) and theresulting mixture was stirred at room temperature for 5 minutes thenheated to 90° C. for 24 h. (nb reaction mixture was followed by TLCusing 5% ethanol/dichloromethane as the eluent). The reaction mixturewas poured into water (800 ml) and this beaker was placed in theultrasonic bath for 2 hours to break up the material. The mixture wasstirred for a further 2 hours then filtered. The residue was washed withwater and then hexane and dried at the pump for 2 hours. The crudeproduct, a brown solid, was heated with acetone (3×400 ml) and filtered.The product was insoluble in most organic solvent. The impurities wereremoved by washing with acetone. The product,4,4′-bis(3-formylcarbazol-9-yl)biphenyl, (7.92 g, 87%) was obtained withmelting point 295° C. (dec.). Found: C, 81.74; H, 4.71; and N, 4.45.C₃₈H₂₈N₂O₂.(CH₃)₂CO requires C, 82.25; H, 5.05; N, 4.68%). ¹H n.m.r.(300 MHz, Me_(e)SO): δ 10.09 (2H, s, CHO); 8.88 (2H, d, J 0.88 Hz,aromatic H); 8.41 (2H, d, J 7.61 Hz, aromatic H); 8.41 (4H, d, J 8.49.Hz, aromatic H); 8.00 (2H, dd, J 8.49, 1.46 Hz, aromatic H); 7.83 (4H,d, J 8.49 Hz, aromatic H); 7.38-7.61 (8H, m, aromatic H).λ_(max)(CH₂Cl₂): 215 nm (ε/Lmol⁻¹ cm⁻¹ 9163), 241 (68 488), 272 (65928), 294 (67 194) 328 (42 620). FT-IR (solid): 3045, 2825, 2730, 1682,1623, 1591, 1505, 1456, 1438, 1365, 1319, 1275, 1230, 1180, 802, 745cm⁻¹.

iii) Synthesis of the 4,4′-bis(3-(hydroxymethyl)carbazol-9-yl)biphenyl(10c)

Sodium borohydride (2.40 g, 63.4 mmol)) was added to the4,4′-bis(3-formyl-carbazol-9-yl)biphenyl (3.42 g, 6.33 mmol) in THF (1.2L) and the resulting suspension was stirred at room temperature for 24h. (The reaction was followed by TLC using 5% ethanol/dichloromethane asthe eluent). Once the reaction was complete, the mixture was slowlypoured into water (400 ml) and the mixture was left to stir at roomtemperature for a further 30 min. The reaction mixture was acidified topH 1 with hydrochloric acid (5M). The product was extracted withdichloromethane (3×300 ml). The combined organic phase was washed withwater (400 ml) and brine (400 ml), dried (MgSO₄), filtered and thefiltrate evaporated to dryness. The crude product, was purified bychromatography on silica using 50% THF/toluene as the eluent. Theproduct was recrystallised from ethanol to give4,4′-bis(3-(hydroxymethyl)carbazol-9-yl) as a pale yellow solid (3.22 g,94%) with m.p. 268° C. (dec.). Found: C, 82.51; H, 4.64; and N, 4.86.C₃₈H₂₈N₂O₂.EtOH requires C, 81.33; H, 5.80; N, 4.74%). ¹H n.m.r. (300MHz, Me₀SO): δ 8.23 (2 H, d, J 7.61 Hz, aromatic H); 8.18 (2H, s,aromatic H); 8.06 (4H, d, J 8, 19 Hz, aromatic H); 7.75 (4H, J 8, 19 Hz,aromatic H); 7.38-7.50 (8H, m, aromatic H), 7.29 (2H, m, aromatic H);5.25 (2H, t, J 5.58 Hz, OH); 4.68 (4H, d, J 5.56 Hz, CH₂).λ_(max)(CH₂Cl₂): 216 nm (ε/Lmol⁻¹ cm⁻¹ 177 455), 240 (57 873), 271 (56595), 294 (55 330) 329 (37 758). FTIR (solid): 3343, 1604, 1500, 1485,1455, 1362, 1330, 1230, 803, 745 cm⁻¹.

iv) Synthesis of 4,4′-bis(3-(allyloxymethyl)carbazol-9-yl) (10)

DMSO was dried over calcium hydride, then distilled under vacuum andstored over molecular sieves.

Potassium hydroxide (2.07 g, 36.9 mmol) was added to DMSO (20 ml) andwas stirred under nitrogen at room temperature for 15 min. The diol(2.39 g, 4.39 mmol) in DMSO (20 ml) was then added, followed by allylbromide (2 ml, 2.80 g, 21.7 mmol) and the resulting mixture was stirredat room temperature under nitrogen overnight. The reaction mixture waspoured into water (200 ml) and the product was extracted intodichloromethane (3×50 ml). The organic phases were combined and werewashed with water (5×150 ml), brine (200 ml) and dried over magnesiumsulfate. The mixture was filtered and the filtrate was evaporated todryness. The material was purified by chromatography on silica usingdichloromethane as the eluent. The relevant fractions were combined andthe solvent removed under reduced pressure. The product was trituratedfrom dichloromethane and hexane to give the product as a pale yellowsolid with melting point 118-120° C. (Found: C, 82.51; H, 4.64; and N,4.86. C₃₈H₂₈N₂O₂.EtOH requires C, 81.33; H, 5.80; N, 4.74%). ¹H n.m.r.(300 MHz, Me₂SO): δ 8.13-8.20 (4H, m, aromatic H); 7.87-7.93 (4H, m,aromatic H); 7.65-7.72 (4H, m, aromatic H); 7.40-7.65 (8H, aromatic H);7.27-7.35 (2H, m, aromatic H); 5.93-6.09, (2H, m, CH═CH), 5.30-5.39 (2H,m, CH═CH); 5.20-5.29 (2H, m, CH═CH); 4.74 (4H, s, CH₂); (8H, m,CH₂—CH═CH₂). λ_(max)(CH₂Cl₂): 241 nm (ε/Lmol⁻¹ cm⁻¹ 88 506), 296 (40331), 319 (29657). FT-IR (solid): 3047, 2852, 1604, 1500, 1455, 1359,1331, 1230, 1074, 915, 807, 759 cm^(−1.)

Example 2

OLED Device Fabrication and Results

OLED devices were made using different combinations of thiol and ene. Inthe following examples the thiols were compounds 24 and MAT1 and theenes were compounds 10, 22, and NME1. Tables 1 and 2 show the specificcombinations that were used. The procedure for fabricating the devicesis as follows.

Ir(ppy)₃ (8 wt %), Thiol and Ene were dissolved in pure chloroform attotal concentration 5-7 mg ml⁻¹. The solutions were spun onto ITO coatedglass substrates (previously cleaned by ultrasonication in commercialdetergent and thorough rinsing with DI water). Prior to spin-coating thedry ITO coated glass was plasma-treated in an Emitech K1050X plasma unit(process gas oxygen, 100 W, 2 min). Solutions were spun onto the ITOsubstrates at 2000 rpm with acceleration 500 rs⁻¹ for a total of 30 sgiving an emitting organic layer of thickness ca 50 nm. Films were thenphotopolymerized under an inert atmosphere (N₂) using a Hanovir UVA 250WUV source. The films were irradiated for 6-8 minutes through a 5″×5″glass photo mask (cut-off 360 nm) giving a rectangular exposed area15×20 mm. Overlap of this area with ITO anode and deposited aluminiumcathode defines active areas consisting of 6 pixels measuring 4×5 mm.The photopolymerized films were developed by rinsing with pure toluene,dried under a stream of dry nitrogen and transferred to the evaporator(KJLesker) for completion of the OLED by evaporation of ETL/HBL and topelectrode. TPBI deposited by vacuum evaporation formed the ETL/HBL (50nm). LiF (1.2 nm) and Aluminium (100-150 nm) deposited by vacuumevaporation formed the cathode.

The device results are shown in tables 1 and 2.

TABLE 1 shows the device performance at a luminance of 100 cd/m² 100cd/m² Op. mass (mg) ratio EQE PE V Device Thiol Ene thiol:ene:dopant(cd/A) (lm/W) (V) 1 24 22  9.4:10.3:1.3 0.90 0.28 10.2 2 24 NME17.8:1.9:0.8 2.02 1.01 6.3 3 MAT1 10 1.8:8.0:0.8 9.95 3.12 10.0 4 MAT1 101.8:8.0:0.8 8.22 3.49 7.4

TABLE 2 shows the maximum device efficiencies for each device Max MaxMax L EQE Corr. L PE Corr. L ToV (@V) CIE Device Thiol Ene (cd/A)(cd/m²) (lm/W) (cd/m²) (V) (cd/m²) x, y 1 24 22 1.0 40 0.42 7.5 6.0 2560.34, (15.0) 0.59 2 24 NME1 2.03 75.9 1.05 62.7 4.8 277 0.33,  (8.0)0.53 3 MAT1 10 — — — — 6.8 265 0.32, (15.0) 0.61 4 MAT1 10 — — — — 5.2911 0.33, (10.0) 0.61

Device 1 is an example of a combination of a charge transporting thiol(24) and a charge transporting ene (22) doped with Ir(ppy)₃.

Device 2 is an example of a combination of a charge transporting thiol(24) and a tetra-functional non-charge transporting ene (NME1) dopedwith Ir(ppy)₃.

Devices 3 and 4 are examples of a combination of a non-chargetransporting tetra-functional thiol (MAT1) and a charge transporting ene(10) doped with Ir(ppy)₃.

Films containing the liquid monomer MAT1 cure quickly, and produce themost efficient devices. It was found that films containing a liquidmonomer and a solid monomer tend to cure quicker than films in whichboth monomers are solid, so it can be advantageous to use a liquid/solidmonomer combination. All of these combinations cure without the additionof a separate initiator to the formulation.

1. A composition comprising a mixture of at least one monomer with theformula:A-(X)_(n)  (1) and at least one monomer with the formula:B—(Y)_(m)  (2) where monomers of formula (1) are polymerisable withmonomers of formula (2), n and m are integers greater than or equal to2, such that n and m may be the same or different, X is a groupcontaining a terminal thiol, Y is a group containing a reactiveunsaturated carbon-carbon bond, each X may be the same or different,each Y may be the same or different, and A and B are molecular fragmentssuch that at least one of A or B is an organic charge-transporting ororganic light-emitting fragment, said mixture further comprising atleast one of an emissive dopant and a charge transporting dopant.
 2. Acomposition according to claim 1, wherein n+m>4.
 3. A compositionaccording to claim 1, wherein A, B, X, and Y do not contain any carbonylgroups.
 4. A composition according to claim 1, wherein at least one of Aand B is a hole-transporting molecular fragment.
 5. A compositionaccording to claim 1, wherein at least one of A and B is anelectron-transporting molecular fragment.
 6. A composition according toclaim 1, wherein at least one of A and B is a bipolar-transportingmolecular fragment.
 7. A composition according to claim 1, wherein atleast one of A and B is a luminescent molecular fragment.
 8. Acomposition according to claim 1, further comprising an initiator.
 9. Acomposition according to claim 1, wherein A in the monomer of theformula 1 comprises a group of the formula

wherein Ar is an optionally-substituted aromatic group and each of Ar₁,Ar₂, Ar₃ and Ar₄ is, independently, an optionally-substituted aromaticor optionally-substituted heteroaomatic group and Ar₁ and Ar₂ and/or Ar₃and Ar₄ may, optionally, be linked together to form, with the N atom towhich they are attached, a N-containing ring, wherein at least two ofAr₁, Ar₂, Ar₃ and Ar₄ are bonded, optionally via a spacer unit, to thegroup X.
 10. A composition according to claim 9, wherein A in themonomer of the formula 1 comprises at least one group of the formula


11. A composition according to claim 10, wherein The monomer of theformula I has the formula


12. A composition according to claim 9, wherein Ar comprises biphenyl.13. A composition according to claim 1, wherein B in the monomer of theformula 2 comprises a group of the formula

wherein Ar is an optionally-substituted aromatic group and each of Ar₁,Ar₂, Ar₃ and Ar₄ is, independently, an optionally-substituted aromaticor optionally-substituted heteroaromatic group and Ar₁ and Ar₂ and/orAr₃ and Ar₄ may, optionally, be linked together to form, with the N atomto which they are attached, a N-containing ring, wherein at least two ofAr₁, Ar₂, Ar₃ and Ar₄ are bonded, optionally via a spacer unit, to thegroup Y.
 14. A composition according to claim 13, wherein B in themonomer of the formula 2 comprises at least one group of the formula


15. A composition according to claim 14, wherein the monomer of theformula 2 has the formula


16. A composition according to claim 13, wherein Ar comprises biphenyl.17. A solid film comprising a thermally-induced or radiation-inducedpolymerisation reaction product of a composition according to claim 1.18. An organic light emitting device comprising laminated in sequence asubstrate, an electrode, a first optional charge transporting layer, anemissive layer, a second optional charge transporting layer and acounter electrode wherein at least one of the emissive layer, the firstoptional charge transporting layer or the second optional chargetransporting layer is a film according to claim
 17. 19. A process forforming a device as claimed in claim 18 that comprises the steps of: i)depositing a film of a composition comprising a mixture of at least onemonomer with the formula:A-(X)_(n)  (1) and at least one monomer with the formula:B—(Y)_(m)  (2) where monomers of formula (1) are polymerisable withmonomers of formula (2), n and m are integers greater than or equal to2, such that n and m may be the same or different, X is a groupcontaining a terminal thiol, Y is a group containing a reactiveunsaturated carbon-carbon bond, each X may be the same or different,each Y may be the same or different, and A and B are molecular fragmentssuch that at least one of A or B is an organic charge-transporting ororganic light-emitting fragment, said mixture further comprising atleast one of an emissive dopant and a charge transporting dopant; andii) polymerising said composition.
 20. A process according to claim 19,comprising exposing at least portions of the film of said composition toactinic radiation to polymerise the corresponding portions of the film.21. A process according to claim 20, comprising exposing the film toactinic radiation through a mask and then developing the film to removethe unexposed portions of the film.
 22. A device as in claim 18, whereinthe light emitting layer contains an emissive dopant.
 23. An organiclight emitting device comprising laminated in sequence a substrate, anelectrode, a first optional charge transporting layer, an emissivelayer, a second optional charge transporting layer and a counterelectrode wherein the emissive layer is a film according to claim 17.24. A process for forming a device as claimed in claim 23 that comprisesthe steps of: i) depositing a film of a composition that is capable ofemitting light of a first colour said composition comprising a mixtureof at least one monomer with the formula:A-(X)_(n)  (1) and at least one monomer with the formula:B—(Y)_(m)  (2) where monomers of formula (1) are polymerisable withmonomers of formula (2), n and m are integers greater than or equal to2, such that n and m may be the same or different, X is a groupcontaining a terminal thiol, Y is a group containing a reactiveunsaturated carbon-carbon bond, each X may be the same or different,each Y may be the same or different, and A and B are molecular fragmentssuch that at least one of A or B is an organic charge-transporting ororganic light-emitting fragment, said mixture further comprising atleast one of an emissive dopant and a charge transporting dopant; ii)exposing portions of said film to actinic radiation through a mask topolymerise the corresponding portions of the film; iii) removingunexposed portions of said film to leave a pre-determined pattern; iv)depositing a film of said composition that is capable of emitting lightof a second colour; and v) exposing portions of said second colour filmto actinic radiation through a mask to polymerise the correspondingportions of the film.
 25. A device as in claim 23, wherein the lightemitting layer contains an emissive dopant.
 26. A process for forming adevice as claimed in claim 23 that comprises the steps of: i) depositinga film of a composition comprising a mixture of at least one monomerwith the formula:A-(X)_(n)  (1) and at least one monomer with the formula:B—(Y)_(m) (2) where monomers of formula (1) are polymerisable withmonomers of formula (2), n and m are integers greater than or equal to2, such that n and m may be the same or different, X is a groupcontaining a terminal thiol, Y is a group containing a reactiveunsaturated carbon-carbon bond, each X may be the same or different,each Y may be the same or different, and A and B are molecular fragmentssuch that at least one of A or B is an organic charge-transporting ororganic light-emitting fragment, said mixture further comprising atleast one of an emissive dopant and a charge transporting dopant; andii) polymerising said composition.
 27. A process according to claim 26,comprising exposing at least portions of the film of said composition toactinic radiation to polymerise the corresponding portions of the film.28. A process according to claim 27, comprising exposing the film toactinic radiation through a mask and then developing the film to removethe unexposed portions of the film.
 29. A solid film comprising aradiation-induced polymerisation reaction product of a compositionaccording to claim 1 that has a pre-determined pattern.
 30. An organiclight emitting device comprising laminated in sequence a substrate, anelectrode, a first optional charge transporting layer, an emissivelayer, a second optional charge transporting layer and a counterelectrode wherein at least one of the emissive layer, the first optionalcharge transporting layer or the second optional charge transportinglayer is a film according to claim
 29. 31. A device as in claim 30,wherein the light emitting layer contains an emissive dopant.
 32. Anorganic light emitting device comprising laminated in sequence asubstrate, an electrode, a first optional charge transporting layer, anemissive layer, a second optional charge transporting layer and acounter electrode wherein the emissive layer is a film according to 29.33. A device as in claim 32, wherein the light emitting layer containsan emissive dopant.